When it comes to his personal investments, Larry Ellison the visionary often gets the better of Lawrence J. Ellison the businessman. The chairman of Oracle Corp. has spent more than $500 million of his own money on 30 or so investments in e-commerce, network appliances, and biotechnology. But few of his personal investments have turned into barn-burners--not yet, anyway. Ellison doesn't seem to mind, though. His 24% stake in Oracle is where he makes his money. Beyond that, he indulges himself.

Ellison is playing a game that's only for the rich. He can afford to bet early and wait for years for a company to blossom. For others, his advice is simple: ''Stick to companies with profits.'' His own investments are about doggedly pursued ideas, not sure-fire returns.

GOOD FIGHT. Case in point: so-called network computers. Five years ago, Ellison proposed a low-cost device for accessing the Net, which he predicted would turn PCs into dinosaurs. Despite a flood of publicity, the devices never took off. Ellison thinks it was just an idea ahead of its time. Now he's putting $10 million into something called New Internet Computer Co., which will make non-PC devices. ''I only invest in things I know something about--biotech and the Internet are two of them. Education is the third,'' he says.

It's all about fighting the good fight for something he believes in. Ellison backs cancer research through biotech companies such as SuperGen Inc. of San Ramon, Calif. He bets on technologies that take full advantage of the Internet, such as Salesforce.com of San Francisco, which lets sales reps manage their accounts on the Net. Often, he backs companies whose founders he knows and trusts, like accounting software maker NetLedger.com Inc. in San Mateo, Calif., which is run by a former Oracle engineer, Evan Goldberg.

While he's not overly worried about making quick returns, he's careful with his money. In 1997, Joseph Rubinfeld, president and chairman of SuperGen, needed Ellison's help to acquire the rights to a drug designed to treat pancreatic cancer. Before investing $23 million, Ellison had two chemists and a dozen lawyers scrutinize the young company, says Rubinfeld. It was a smart bet: Ellison has made seven times his initial investment since an IPO in February.

Ellison is a patient investor. In 1988, he bought nCUBE, which builds machines to speed multimedia technologies such as videoconferencing over the Web. For years, it looked like a bust. Today, however, thanks to the growing use of high-speed Net connections, nCUBE has more than 100 customers and is on track for an IPO within a year.

NET CURRENCY. Perhaps the most adventurous Ellison investment is London-based beenz.com, which has created a faux currency for Internet shoppers. Ellison believes this kind of electronic currency can be used more easily and more safely than credit cards. But skeptics abound. ''I'm of the opinion that this is like Disney Dollars,'' says Gene Alvarez, program director for electronic business strategies at market researcher Meta Group Inc. ''They're great in the park. But what do you do after you leave?'' Beenz.com executives insist they are quite different from a handful of Net scrip companies that have come and gone. ''Larry wouldn't have gotten involved, if it was a just a vanilla investment,'' says CEO Philip Letts.

Most importantly, perhaps, the beenz.com Web site is built on an Oracle database. For Ellison, there's nothing plain-vanilla about that.